Smokeless explosive powder and process of making same



Patented May 10, 1927.

UNHTEQ STATEfi FRANCIS I. DU PONT AND ERNEST DU PONT,

ifiZZthZ FATW? OF WILMINGTON, DELAWARE, ASSIGNORS,

BY MESNE ASSIGNMENTS, TO U. S. F. POWDER COMPANY, OF WILMINGTON, DELA- WARE, A CORPORATION OF DELAWARE.

SMOKELESS EXPLOSIVE POWDER AND PROCESS OF MAKING SAME.

No Drawing. Original application filed January 24, 1919, Serial No. 272,857, renewed April 5, 1321,

Serial No. 458,695. 1922. Serial No. 558,252.

The object of our invention is to produce a smokeless explosive powder which, when used as a propellent charge in ordnance, will approximately eliminate, or at least very materially reduce, the muzzle flash. To accomplish this it is necessary that the powder should be substantially consumed before the gaseous mass emerges from the muzzle of the gun. It is not merely sufiicient that the composition and structure of the powder should be such as to promote rapid burning and early combustion, but it is also essential that this rapid burning should be effected without substantial increase of chamber pressure in order thereby to avoid erosion or the gun barrel.

It is the usual practice to efl ect the burn ing of ordnance powder in a progressive way by manufacturing the grains or units with perforations through the grains, so that they will burn from the inside as well as from the outside, thus exposing to the flame, as the burning proceeds, a progressively increasing superficial area. There is a progressive acceleration of combustion.

lVe have discovered that the rate of progression and acceleration of the burning in this type ofpowders may be substantially increased, without increase of chamber pressure, by distributing in a colloided mass of nitrocellulose powder a flame propagating agent which will carry the flame from the exposed surfaces, through a multitude of minute progressively developed channels or cavities, into the interior of the powder grains, thereby bringing about an earlier combustion and effecting a more complete consumption of the powder than is the case where reliance is had solely upon relatively largean'd coarse mechanical perforations.

It has been assumed that the flash of light produced at the muzzle of a gun is due to the fact that propellent powders composed substantially entirely of nitrocellulose have an actual deficiency of oxygen below that which would be necessary to burn all of the carbon, or its equivalent in combustible products, and that minute particles of carbon, intensely heated, actually escape from the muzzle of a gun and combine with the oxygen of the atmosphere in precisely the same way as do the particles of carbon in an ordinary flame of illuminating gas.

Renewed October 19, 1921, Serial No. 508,832. This application filed May 3,

lVhile this may be a correct explanation of the phenomenon, longed experiment that it is not essential for our purposes that the ingredients added shall actually contain an excess of oxygen capable of compensating for this excess of carbon. In fact, we have used with equal success one flame propagating agent having an excess of oxygen and another in which there is no oxygen available for the nitrocellulose.

It is not suflicient, however, that the added flame propagating agent shall merely be effective to expedite the consumption of the nitrocellulose, but it must be such an agent as will do this without substantially increasing the chamber pressure, without seriously fouling the gun and without producing an excess of smoke. This not merely materially narrows the range of substances which would be otherwise available, but after the proper substances have been ascertained by experiment, the further problem arises of adding them in proper proportions to the nitroc ellulose. Finally, after this information is acquired, the addition of the flame propagating agent to the nitrocellulose must precede any substantial colloiding of the nitrocellulose.

We have discovered that a mixture of barium nitrate and potassium nitrate, added to soluble nitrocellulose and then colloided, will render it substantially flashless provided the proportions are carefully determined and provided they are properly incorporated.

The characteristics of these two the propagating agents are, of course, quite dissimilar, the most notable difference being that the latter has an excess of ox gen, which is evolved when heated, while t 1e former is a complete explosive and has no available oxygen.

Where a mixture of the two salts above named is used, we prefer to use about twoparts of, the barium salt to one part of the potassium salt,- although these proportions may be varied.- The total of the two ingredients should form referably from about 8 to 12 per cent. of t 1e entire explosive. In no case should it exceed 20 per cent, while we distinctly prefer not to exceed 15 per cent. On the other hand, the proportion may be we have found by proif as low as 4 per cent. and still very materially reduce the flash, although we prefer a minimum of about 7 or 8 per cent. The objection to using a large proportion of this fire propagating agent is that it results in objectionably fouling the gun, and, -more= over, a relatively large proportion produces no useful efifect in the elimination of the flash, this being, for all practical purposes, attained by a relatively small proportion.

The process of adding the flame-propagating agent to the nitrocellulose is of great importance. Unless the agent be so added as to effect a very thorough and intimate association of the particles, the finished powder will give non-uniform and uncertain results as a commercial product, in which uniformity and certainty of action are essential.

In carrying out our process it is necessary, in order to secure certain and uniform results, to thoroughly incorporate the flame ropagating agent with the nitrocellulose Before colloiding. \Ve proceed by taking soluble nitrocellulose and add thereto the specified proportion of the flame producing agent, wet it with about thirty per cent of a suitable blending liquid, such as water or gasoline, and incorporate the same in a standard black powder wheel mill for about an hour or an hour and a quarter. The liquid added should be one which does not chemically combine with the explosive ingredients, or does not combine with them except to form a solution from which the solvent may be expelled by drying or by displacement otherwise. We prefer to use gasoline. Without the thorough moistening of the powder, the mixing operation, in any mill of the kind specified, would be attended with serious danger.

After the in redients are thus thoroughly incorporated, the added liquid, or most of it, is expelled by drying or otherwise and then the colloiding agents, ether and alcohol, are added, and the entire mixture is thoroughly and completely colloided in a kneading machine for about an hour. After the powder has been formed into grains, a considerable proportion of alcohol and ether is distilled off, a certain proportion remaining in the finished product.

The removal should not be effected in any way which will cause the removal of the fire carrying agent, as that would produce a certain undesirable porosity in the finished powder, whereas porosity, or porosityalone, is not the result desired, but rather a proper dissemination of .the fire propagating agent through the colloided nitrocellulose. -'The thorou h in corporation of the ingredients is of t e utmost importance, and it seems to be practically essential to first thoroughly incorporate the fire propagating agent'with the nitroof the alcohol and ethercellulose and afterward colloid: in other words, to rather closely adhere to the procedure above described.

The resultant powder is, to all intents and purposes, fouling of the gun, and the smoke produced isbfo limited in volume as to beunobjectiona e.

We do not herein claim, broadly, the addition of black powder, barium and potassium nitrates, or other flame propagating agents, to any of the so-called smokeless or semi smokeless powders, as these have been added in other proportions and in other ways and for other purposes to certain of such explosives. In our invention, the bodies are associated in a particular way.

While we have herein described black powder, barium and potassium nitrates as illustrative of a suitable flame-propagating agent, it is herein intended to restrict the claims to that specific embodiment of the invention comprising the use of barium ni-, trate and Ipotassium nitrate. In another application 376,267, we have claimed the use of a flamepropagating agent broadly and have also claimed the use of black powder specifically.

Having now fully described our invention, what we claim and desire to protect by Letters Patent is:

' l.- The process of making flashless smokeless propellent powder which comprises adding to and thoroughly incorporating barium nitrate and potassium nitrate with soluble nitrocellulose, and afterward completely colloiding said nitrocellulose with ether and alcohol to produce a homogeneous said barium nitrate and body retaining the distributed through the potassium nitrate finished explosive.

2. The process of making smokeless propellent powder which comprises adding barium nitrate and potassium nitrate to soluble nitrocellulose, moistening with a suitable liquid and thoroughly incorporating, expelling the liquid, and afterward collo ding with ether and alcohol.

3. The process of making flashless explosive powder which comprises so mixing soluble nitrocellulose with barium nitrate and potassium nitrate and a nitrocellulose colloiding agent that the action of the colloiding agent will take place substantially after distribution of the said nitrates throughout the nitrocellulose, and forming the colloided nitrocellulose into grains, whereby the colloided cellulose grains will be intercellularly impenetrated with the said nitrates and the rapid combustion of the latter will carry the flame rapidly from the exposed surfaces into-the interior of the grains and effect a relatively early complete consumption of the powder.

4. The process of making flashless flashless, there is no serious led April 24, 1920, as Serial No.-

smokeless propellent powder which comnitrocellulose containing four to twenty per 15 prises adding to and thoroughly incorpocent of a mixture of the nitrates-of barium rating with soluble nitrocellulose between and potassiumdistributed therethrough. four and twenty per cent of a mixture of the 7. A flashless smokeless propellent pow 5 nitrates of barium and potassium and comder, which comprises completely colloided pletely colloiding said nitrocellulose. nitrocellulose containing ei ht to twelve per 2 5 The process of making .flashless cent of a mixture of the nitrates of barium smokeless propellent powder which comandv potassium. prises adding to and thoroughly incorpo- In testimony of which invention, we have 10 rating with soluble nitrocellulose from eight hereunto set our hands, at Wilmington, on

to twelve per cent of a mixture of the nitrates this 22nd day of January, 1919. of barium and potassium. 6. A flashless smokeless propellent pow- FRANCIS I. DU PONT.

der, which comprises completely colloided ERNEST DU PONT. 

